Mount assembly for electron tubes



Dec. 29, 1953 H. K. ISHLER' MOUNT ASSEMBLY FOR ELECTRON TUBES Filed Feb. 11, 1952 INVENTOR HARRY K. ISHLER yway ATTORNEY Patented Dec. 29, 1953 ENr OFFICE MOUNT ASSEMBLY FOR ELECTRON TUBES Harry K. Ishler, Lansdale, Pa., assignor to Philco Corporation, Philadelphia,

of Pennsylvania -Pa., a corporation Application February 11, 1952, Serial N 0. 271,029 12 Claims. (Cl. 313-261) This invention relates to electron discharge tubes and more particularly to tubes of the concentric electrode kind;

A principal object is to provide a novel mount construction for electron tubes employing an indirectly heated cathode, and wherein maximum accuracy of interelectrode spacings and ruggedness of assembly are obtained.

Another object is to provide an improved interelectrode spacing arrangement for multi-electrode tubes which permits the achievement of very low interelectrode leakages.

Another object is to provide an improved electron tube mount having a radiantly heated tub lar cathode.

A feature of the invention relates to an electron tube of the kind employing an indirectly heated or radiantly heated cathode whose radio of diameter to length is large, and yet the oathode and heater unit as a whole is rigidly supported and accurately centered with respect to one or more surrounding electrodes.

Afurther feature relates to the novel organization, arrangement and relative locations of parts which cooperate to provide an improved electron tube of the indirectly heated cathode kind."

7 Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

In the drawing Fig. 1 is an elevational view of a tube embodying features of the invention, with the enclosing bulb partly broken away to show the-interior construction.

Fig. 2 is a plan sectional view of Fig. 1 taken along-the line 2-4 thereof.

Fig. 3 is a greatly magnified sectional view of part of Fig. l alongthe line 3-3 thereof, showing the relative radial spacings between the various electrodes and concentric elements of Fig.1.

While the invention is not limited to any particular design or shape of electron tube bulb, it

is shown for illustration in the drawing as em bodied in a bulb of one: well knowndesign. The

bulb lfl which may be of glass or other suitable its lower end by any ll through These materi l is closed off at wellknown formi'ofstem or header which are, sealedthevarious prongs l2. prongs interiorlyof the tube are connected to the various electrodes and actaas the lead-in mem-'-. bars as well, as supports for the. electrode mounti Preferably they have welded to their inner ends short. metal extensions? l3iwhichican be bent to Inaccordance with the invention the mount comprises a tubular metal cathode sleeve l4 whose internal diameter is much greater than the diameter of the centrally located heating element l5, thus providing comparatively large radial spacing between the said heater element and the internal surface of sleeve M. In other words, the sleeve I 4 is arranged to be heated substantially entirely by heat radiated from the said heater. It becomes important, therefore, to make sure that the heater unit is accurately centered and maintained centered with respect to the cathode sleeve sothat all areas of that sleeve receive substantially uniform radiant heat. For this purpose the heating unit comprises a rigid metal rod l6, for example of molybdenumv or similar refractory metal or alloy. This metal rod has integrally applied thereto by any suitable process, an insulating coating I! of substantial thickness. This coating may be of any well known ceramic insulating material such as is conventionally used. in cathode heater constructions. Helically wound around the external surface of the ceramic coating 16 is a heater wire l8 of tungsten, or the like, which is welded at its lower end to one of the prongs [2. The opposite end of the heater wire I8 is Welded to a point adjacent the upper end of rod [6, and for this purpose the said rod is free from ceramic at that particular region. The tip of rod 16, however, has the ceramic coating for purposes to be described. Rod to a corresponding one of the prongs 12 so that heating current can be supplied to the wire [5 toraise it to a suitable incandescent temperature. Thus,- the heater unit is rigidly and centrally supported Within the bulb [0. In accordance withwell known procedures the external surface of the sleeve 14 is provided with a coating I9 of any well known thermionic orelectronic emitting material, such as is used in electronic tubes generally.

It will be seen from the foregoing that because of the relatively large diameter 'ofthe cathode sleeve M, as compared with the diameter of the heater element. the cathode unit is massive, and there arises the problem of supporting this cathode unit in such a way that it does not change its concentric position within the tube even when subjected to relatively heavy shocks. This problemis of even greater importance when the cathode unit is to cooperate with a surrounding grid or electrode which is extremely closely spaced from the cathode. For example. in one particular kind of-tubeto which '1 I6 is welded at its lower end 7 comparatively :fi' the invention is applicable, the heater rod l6 has a diameter of 0.030 inch, the ceramic coating 11 had a diameter of 0.056 inch and the tungsten wire 18 was 0.003 inch diameter. Thus, the heater unit as a whole had an approximate outside diameter of 0.62 inch, while the sleeve 14 had an internal diameter of 0.250 inch, and the first surrounding grid 20 had an internal diameter of 0.260 inch. In other words, the spacing between the cathode surface and the next adjacent elec trode or grid is very small in comparison with the diameter of the cathode sleeve. This same problem of maintaining the desired permanency of concentricity also afiects the remaining surrounding electrodes such, for example, as the second grid 2 i, the third grid 22, and the tubular metal plate or anode 23.

In accordance with the invention, the various electrodes and elements are spaced apart at their upper ends by a series of centrally apertured insulator discs 24, 25, 26, 21, 28. Preferably all the elements l4-23 are assembled together'to form a single rigid unit. For this purpose there are provided two main vertical side rods 29, 39 which are welded at their lower ends to respective prongs l2. The lower ends of the various elements are spaced apart by means of an insulator dis-c SI of mica, or the like, having a pair of diametrically opposite holes through which the said rods 29, 30 pass.

' The said mica disc 31 may be supported at the desired point on the side rods 29, 30 by resting, for example, on a pair of metal tabs 32, 33 welded to the side rods. The plate or anode 23 has diametrically opposite tubular flanges 34, 35 which telescope over the respective side rods 29, 30. Preferably also'these flanges extend downwardly below the lower edge of plate 23 and extend upwardly above the upper edge of plate 23, and these extending flange ends abut respectively against the lower mica 3i and the upper mica 28.

This provides respective clearances between the lower and upper edges of the plate and the respective mica discs 31, 28. The mica disc 28 is held in place by respective metal tabs .31, 3'! welded to side rods 29, 30. The grid electrodes 20, 2|, and 22 are supported attheir lower ends on the mica disc 31' and are provided with respective integrally shouldered tabs which pass through corresponding holes in the mica disc 3|,

and these tabs are welded to corresponding prongs E2. The mica disc3| has a central cir cular opening which closely fits the external diameter of the cathode sleeve l4, and in order to support the said sleeve it may be provided witha raised peripheral rib or bead 38 which abuts against the mica 3!.

Mica discs 24-28 have respective central circular openings to receive respectively the upper ends of theheater element l5, the cathode sleeve M, the first grid 20, the second grid 2i, and the third grid 22. micas are accurately punched or'cut so as to provide a close fit with the end of the corresponding electrode, it being understood, of course, that the openings in the successive mica discsare of successively greater tive electrode ends.

These openings in the respective size to accommodate the respec- It will also be observed that these discs 2i-28 are spaced vertically from each 1 other and the ends of the various electrodes are of successively greater length or stag ered-9S0 that, for example, the third grid 22 just passes does not con- Lilsewise' the through the opening in disc 28 but tact the next superposed disc 21.

second arid 2i; just passes through the openingthe respective electrodes, very low interelectrode I leakages exist, since each electrode contacts only a single mica spacer as compared with the condistance on the side rods 4 in the corresponding disc 21 but does not reach the next superposed disc 25. Similarly the first grid 20 just passes through the corresponding opening in disc 26 but does not reach the next disc 25. Likewise the cathode sleeve [4 just passes through the opening in the disc 25 but does not reach the disc 24. Finally, the ceramic coated end of the heater element l5 just passes through the corresponding opening in the disc 24. These discs can be spaced apart the required 29, 30 by respective metal tabs welded to said side rods, the uppermost tabs 38, 39 being the last to be welded in place against thedisc 24, thus holding all the elements of the mount together as a rigid unit.

- aligned grid openings which are also aligned with the said fiutings. Thus, the electrons from the various fluted areas of the cathode form respective beams which pass through the respective aligned openings in the grids to reach the anode It will be understood, of course, that the invention is not limited to any particular structure for the grids 20-22. Preferably, however, these grids are formed as respective seamless metal tubes of minimum wall thickness and having a multiplicity of grid openings which are regularly and uniformly spaced from each other. Thus, the electrons from the cathodes strike the anode 23 in the form of a corresponding multiplicity of 1 pyramidal or conical beam elements.

Apart from the mechanical structural rigidity and accuracy of spacing which results from the foregoing described embodiment there are a number of improved results that are obtained according to the invention. Thus, by providing the relatively large free space between the heater element I5 and the large diameter cathode sleeve [4 it is possible to evacuate the bulb l0 much faster than is possible'with the conventional closely spaced heater and cathode sleeves. Furthermore, the use of a large diameter cathode and corresponding large diameter surrounding electrodes permits the use of tabs on these electrodes at their lower ends which can be used to facilitate automatic concentric alignment of the various electrodes on automatic assembly machines and the like. Further, these tabs can be located on the large diameter electrodes so that the distance between the tabs can be greater than in conventional tubes where the grid electrodes are supported by conventional side rods.

The invention also insures the same transit time for all electrons passing between the cath- Ode and one or more of the surrounding electrodes, thus enabling the tube to function more efficiently in high frequency circuits. A more uniform amplification factor is obtained over the entire area of the cathode, thus making possible a very sharp 'plate-current-cut-off characteristic. Furthermore, by using the superposed upper micas and the particular manner oftheir cooperation with the staggered upper ends of scribed construction ventional; construction wherein each electrode contacts the same spacer and the leakag path 'is fixed by the actual radial distance between Furthermore, with the dea very high mutual conductance per milliampere of plate-current is possiblebecause the space current is uniform over the, entire cathode area. i

.While one particular embodiment has been described herein, it will be understood that variouschanges and modifications can be made therein: without departing from the spirit and scope of the invention. l

-What is claimed is:

1'. An electrode assembly for electron tubes and the, like, comprising in combination, a plurality of radially spaced electrodes, and means to maintain said electrodes accurately spaced, said .means including a plurality of spaced insulator discs each having a central opening which closely fits around and engages the end of only a corresponding one of said electrodes, said electrodes having their corresponding ends staggered longitudinally with relation to each other and correlated with the spacing between said discs whereby the said end of each electrode contacts only a corresponding one of said discs.

2. An electrode assembly for electron tubes and the like, comprising in combination, a plurality of cylindrical electrodes to be maintained in predetermined radially spaced relation, and means to maintain said spaced relation including a plurality of insulator discs extending transversely to the common axis of said electrodes, each of said discs having a central opening corresponding in diameter to the diameter of only a particular one of said electrodes which closely fits therein and passes therethrough, said electrodes surrounding each other and being of successively larger diameter and having their respective ends which pass through said respective openings of staggered length, and means to support said discs in superposed planar parallelism.

3. An electrode assembly for electron tubes and the like, comprising in combination, a plurality of concentric spaced tubular electrodes, a pair of parallel uprights, a plurality of insulator spacer discs extending between side uprights and anchored thereto in superposed parallel spaced relation, each of said discs havin a single respective central opening to receive and engage the end of only a single corresponding one of said electrodes, and means to support said electrodes in spaced relation at their other ends 4. An electrode assembly for electron tubes and the like, comprising in combination, a plurality of cylindrical lectrodes to be maintained in accurate and permanent concentric relation, insulator spacer means cooperating with the lower ends of said electrodes to hold them in spaced relation, and other insulator spacer means cooperating with the upper ends of said electrodes to hold them in spaced relation, the last mentioned means comprising a plurality of insulator discs, means to support said discs in spaced relation transversely to the length of said electrodes, each of said discs having a central opening within which is closely fitted and which engages the end of only one of said electrodes.

5. An electrode assembly for electron tubes and the like, comprising a series of concentric surrounding tubular electrodes, insulator means for supporting said electrodes in spaced relation adjacent one end, the opposite ends of said elecsuccessive electrodes.

trodes beingof staggered lengths, and a series of spaced insulator discs one for eachof the staggered electrode ends, each of said discs having a central opening fitting the corresponding end of only a corresponding one of said electrodes.

6. An electrode assembly for electron tubes and the like, comprising in combination, a pair of parallel uprights, means to support said elec-& trodes at their lower ends in predetermined spaced relation, a plurality of insulator discs extending transversely between the upper ends of said uprights, means to fasten said discs insuperposed spaced relation on said uprights, each of said discs having a central opening with the openings in successive discs of increased size, and a plurality of concentric tubular electrodessup-v ported at their lower ends in spaced relation, said electrodes having their upper ends staggered and with each upper end closely fitted within the central opening of only a corresponding one of said discs.

7- An electrode assembly for electron tubes and the like, comprising atubular cathode'sleeve, a first electrode surrounding said sleeve. 2. second electrode surrounding said first electrode, 1118117- lator means cooperating with the lower endsof. said cathode sleeve and said electrodes to hold them in spaced relation, a first insulator disc having a central opening closely fitting the upper end of said cathode sleeve, means to support said first insulator disc above and out of contact with the upper end of said first electrode, a second insulator disc having a central opening closely fitting the upper end of said first electrode, means to support said second insulator disc above and out of contact with the upper end of said second electrode, a third insulator disc having a central opening which closely fits the upper end of said second electrode, and means to maintain said third disc in predetermined spaced relation below said second disc.

3. An electrode assembly for electron tubes and the like, comprising a tubular cathode sleeve, a central longitudinal rigid heater unit for said sleeve, the diameter of said unit being substantially smaller than the diameter of said sleeve, means attached to the lower end of said unit to support it independently of said sleeve whereby said sleeve is heatable substantially entirely by radiant heat, and means to maintain the upper end of said sleeve and the upper end of said unit in accurate spaced relation, the last mentioned means including a first insulator spacer disc having a central opening closely fitting and engaging the end of said sleeve only, a second insulator spacer disc having a central opening closely fitting and engaging the end of said unit only, and means to hold said first and second discs in superposed spaced parallelism.

9. An electrode assembly according to claim 8, in which at least one tubular grid surrounds said cathode sleeve, and a third insulator disc is provided having a central opening to fit and engage the end of said grid only, and means to support said third disc in spaced parallelism beneath said first disc.

10. A unitary mount assembly for electron tubes and the like, comprising a pair of parallel uprights, a bottom mica spacer, a top mica spacer, each of said spacers extending transversely between said uprights, an anode supported by said uprights and located between said mica spacers, a tubular grid electrode supported at its lower end on said bottom mica, the upper end of said grid closely fitting a corresponding cenan'd' -located between said micas,

7 trait opening in is'aidito mica which calorie it en gages?aifirstzadditional mica spacer mounted in spaced parallelismito saidtop mica spacenan additional. Ltubular electrode of smaller diameter than said gridelectrode supported at its lower end on said bottom mica and closely fitting a corresponding center openingiin said additional mica g l v lL A' unitary mount particularly suitable for automatic-assembly, comprising a pair ofparallel uprights; aioottorn mica spacer, a first top mica spacer, each :of said spacers extending transversely between said uprights and anchored thereto, an: anode also anchored to said uprights a series of tubul'air electrodes of successively smaller diameters surrounded bysaid anode, a second top mica spacer, means to support said second top mica spacer in spaced relation to the first mentioned top rnica' spacer, saidsecondtop mica spacer having a central opening within which is closely fittedaround and engages the upper end of one of said tubularelectrodes alone.

i zi-An electron tube, comprising a central longitiidinal-l-y rigid heater element, comprising a rigid-center rod having an integral coating of i'ns'ulationmaterial, a heater Wire coiled around W saidlinsulation externally theretoi'and connected in series with said center rod to form a rigid unitary heater element, a large diameter cathode sleeve surroundingsaid heater and heated substantiallyientirely by radiant heat, a'series of multi-apertured seamless tubular grids surrounding said sleeve, an anode surrounding sai-digrids, and means to maintainsaid heater, said grids, and said-anode in fixed radial concentric spaced relation; the last mentioned means including a series of physically spaced parallel insulator discs, one ofsaiddiscshaving a central opening to receive and fit around the end of'said heater unit only, each of the remaining discs having a central opening closely fitting the end of a corresponding one of said grid electrodes alone, and a pair of uprights to which said discs are anchored.

HARRY K. ISHLER.

References Cited in the file of this patent UNITED STATES PATENTS Number 

